The more I think about it, the more I think Okoye and the Dora Milaje DID commit treason and rebelled against the King. TChalla never officially yeilded, HOWEVER Killmonger didn’t grant request for a rematch, but technically the fight was still on because: TChalla didn’t die, and TChalla never officially yield. You can say that Forest yeilded for him, but that’s not still an official yeild.
But Killmonger was still declared King. Killmonger never granted a request for a rematch. Okoye rebelled because she thought she that he wasn’t the right fit for king, saying “your heart is evil” or something like that. It’s not in her right to decide whose king or not. Eric won fair and square. There was a technicality but he was still declared king.